Cardiac reinforcement device

ABSTRACT

The present disclosure is directed to a cardiac reinforcement device (CRD) and method for the treatment of cardiomyopathy. The CRD provides for reinforcement of the walls of the heart by constraining cardiac expansion, beyond a predetermined limit, during diastolic expansion of the heart. A CRD of the invention can be applied to the epicardium of the heart to locally constrain expansion of the cardiac wall or to circumferentially constrain the cardiac wall during cardiac expansion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. Ser. No.08/720,556, filed Oct. 2, 1996 now U.S. Pat. No. 5,702,343.

BACKGROUND OF THE INVENTION

The present invention is generally directed to a device and method forreinforcement of the cardiac wall. The invention is particularly suitedfor the treatment of cardiac disease which result in atrial orventricular dilation. The invention provides reinforcement of thecardiac wall during diastolic chamber filling to prevent or reducecardiac dilation in patients known to have experienced such dilation orwho have a predisposition for such dilation occurring in the future. Thecardiac reinforcement structure is typically applied to the epicardialsurface of the heart.

Cardiac dilation occurs with different forms of cardiac disease,including heart failure. In some cases, such as post-myocardialinfarction, the dilation may be localized to only a portion of theheart. In other cases, such as hypertrophic cardiomyopathy, there istypically increased resistance to filling of the left ventricle withconcomitant dilation of the left atria. In dilated cardiomyopathy, thedilation is typically of the left ventricle with resultant failure ofthe heart as a pump. In advanced cases, dilated cardiomyopathy involvesthe majority of the heart.

With each type of cardiac dilation, there are associated problemsranging from arrhythmias which arise due to the stretch of myocardialcells, to leakage of the cardiac valves due to enlargement of thevalvular annulus. Devices to prevent or reduce dilation and therebyreduce the consequences of dilation have not been described. Patchesmade from low porosity materials, for example Dacron™, have been used torepair cardiac ruptures and septal defects, but the use of patches tosupport the cardiac wall where no penetrating lesion is present has notbeen described.

Drugs are sometimes employed to assist in treating problems associatedwith cardiac dilation. For example, digoxin increases the contractilityof the cardiac muscle and thereby causes enhanced emptying of thedilated cardiac chambers. On the other hand, some drugs, for example,beta-blocking drugs, decrease the contractility of the heart and thusincrease the likelihood of dilation. Other drugs includingangiotensin-converting enzyme inhibitors such as enalopril help toreduce the tendency of the heart to dilate under the increased diastolicpressure experienced when the contractility of the heart muscledecreases. Many of these drugs, however, have side effects which makethem undesirable for long-term use.

Accordingly, there is a need for a device that can reduce or preventcardiac dilation and reduce the problems associated with such dilation.

SUMMARY OF THE INVENTION

The present invention is directed to a device and method forreinforcement of the cardiac wall. According to the invention, a cardiacreinforcement device includes a biomedical material which can be appliedto the epicardial surface of the heart and which expands to apredetermined size that is selected to constrain cardiac expansionbeyond a predetermined limit. A biomedical material suitable for acardiac reinforcement device can be an elastic or non-elastic mesh ornon-mesh material.

In one embodiment, a cardiac reinforcement device is a biomedicalmaterial in the form of a patch. The size of the patch is selected tolocally constrain cardiac expansion.

In another embodiment, a cardiac reinforcement device is a biomedicalmaterial shaped as a jacket with a predetermined size selected for thejacket to surround the epicardial surface of the heart andcircumferentially constrain cardiac expansion. In one embodiment, acardiac reinforcement jacket may be applied to the epicardial surfacevia a minimally invasive procedure such as thorascopy.

A cardiac reinforcement jacket can include a securing arrangement forsecuring the jacket to the epicardial surface of the heart. The cardiacreinforcement jacket can also include a mechanism for selectivelyadjusting the predetermined size of the jacket around the epicardialsurface of the heart. The adjustment mechanism can include a slot havingopposing lateral edges which when pulled together decrease thevolumetric size of the jacket. In an alternative embodiment, a selectivesize adjustment mechanism can include an inflatable member mountedbetween the jacket and the epicardial surface of the heart. Inflation ofthe inflatable member provides for reduction in the volumetric size ofthe jacket.

A cardiac reinforcement device of the invention can be used to treatcardiomyopathy or to reduce the diastolic volume of the heart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a frontal view of one embodiment of a cardiac reinforcementpatch.

FIG. 2 is a perspective view of the cardiac reinforcement patch of FIG.1 in place on the epicardium of a heart.

FIG. 3 is a perspective view of one embodiment of a cardiacreinforcement jacket according to the invention.

FIG. 4 is a second embodiment of a cardiac reinforcement jacketaccording to the invention.

FIG. 5 is a perspective view of the embodiment of the cardiacreinforcement jacket shown in FIG. 4 in place around the heart.

FIG. 6 is a schematic cross sectional view of one embodiment of amechanism for selectively adjusting the predetermined size of a cardiacreinforcement jacket.

FIG. 7 is a perspective view of a placement tool which can be used forapplying a cardiac reinforcement jacket.

FIG. 8 is a perspective view of a placement tool being employed to placea cardiac reinforcement jacket over the heart.

DETAILED DESCRIPTION

The present invention is directed to reinforcement of the heart wallduring diastolic filling of a chamber of the heart. The invention isparticularly suited for use in cardiomyopathies where abnormal dilationof one or more chambers of the heart is a component of the disease.

As used herein, "cardiac chamber" refers to the left or right atrium orthe left or right ventricle. The term "myocardium" refers to the cardiacmuscle comprising the contractile walls of the heart. The term"endocardial surface" refers to the inner walls of the heart. The term"epicardial surface" refers to the outer walls of the heart.

The heart is enclosed within a double walled sac known as thepericardium. The inner layer of the pericardial sac is the visceralpericardium or epicardium. The outer layer of the pericardial sac is theparietal pericardium.

According to the present invention, a cardiac reinforcement device (CRD)limits the outward expansion of the heart wall during diastolic chamberfilling beyond a predetermined size. The expansion constraint applied tothe heart by a CRD is predetermined by the physician based on, forexample, cardiac output performance or cardiac volume. In contrast toknown ventricular assist devices which provide cardiac assistance duringsystole, a CRD according to the present disclosure provides cardiacreinforcement during diastole.

A CRD is made from a biomedical material which can be applied to theepicardial surface of the heart. As used herein, a "biomedical material"is a material which is physiologically inert to avoid rejection or othernegative inflammatory response. A CRD can be prepared from an elastic orsubstantially non-elastic biomedical material. The biomedical materialcan be inflexible, but is preferably sufficiently flexible to move withthe expansion and contraction of the heart without impairing systolicfunction. The biomedical material should, however, constrain cardiacexpansion, during diastolic filling of the heart, to a predeterminedsize. Examples of suitable biomedical materials include perforate andnon-perforate materials. Perforate materials include, for example, amesh such as a polypropylene or polyester mesh. Non-perforate materialsinclude, for example, silicone rubber.

A biomedical material suitable for a device of the invention generallyhas a lower compliance than the heart wall. Even though the biomedicalmaterial is less compliant than the heart wall, some limited expansionof an elastic biomedical material can occur during cardiac filling.

In an alternative embodiment, the biomedical material can besubstantially non-elastic. According to this embodiment, the term"substantially non-elastic" refers to a material which constrainscardiac expansion during diastole at a predetermined size, but which hassubstantially no elastic properties.

Regardless if the biomedical material is elastic or non-elastic,advantageous to a CRD according to the present disclosure is cardiacreinforcement which is provided during diastole. Moreover, a CRD asdisclosed herein does not provide cardiac assistance through activepumping of the heart.

I. CRD Patch

In one embodiment, a cardiac reinforcement device (CRD) provides forlocal constraint of the heart wall during cardiac expansion. Accordingto this embodiment, a CRD is a "patch" that provides reinforcement ofthe heart wall at a localized area, such as a cardiac aneurysm or at anarea of the myocardium which has been damaged due to myocardialinfarction. When discussing a "patch", "predetermined size" of the patchmeans that the size of the patch is selected to cover an area of theepicardial surface of the heart in need of reinforcement withoutcompletely surrounding the circumference of the heart.

A CRD patch can be prepared from the biomedical materials describedabove. In a preferred embodiment, the patch is an open mesh material.

A CRD patch can be applied to the epicardial surface of the heart overor under the parietal pericardium. A patch is typically applied to theepicardial surface by suturing around the periphery of the patch. Theperipheral edge of the patch can include a thickened "ring" or otherreinforcement to enhance the strength of the patch at the point ofsuture attachment to the epicardium. Generally, a patch is applied tothe epicardium through a thoracotomy or other incision providingsufficient exposure of the heart.

II. CRD Jacket

In another embodiment, a CRD is a jacket that circumferentiallysurrounds the epicardial surface of the heart. When applied to theheart, a CRD jacket can be placed over or under the parietalpericardium.

A CRD applied to the epicardium is fitted to a "predetermined size" forlimitation of cardiac expansion. According to a jacket embodiment,"predetermined size" refers to the predetermined expansion limit of thejacket which circumferentially constrains cardiac expansion duringdiastolic filling of the heart. In practice, for example, a physiciancould measure cardiac output and adjust the jacket size to an optimalsize for the desired effect. In this example, the optimal size is the"predetermined size". In one embodiment, the predetermined size can beadjusted for size reduction as the cardiac size is reduced.

In one embodiment, the CRD jacket is a cone-shaped tube, having a basebroader than the apex, which generally conforms to the external geometryof the heart. When applied to the epicardial surface of the heart, thebase of the jacket is oriented towards the base of the heart, and theapex of the jacket is oriented towards the apex of the heart. Typically,the base of the jacket includes an opening for applying the jacket bypassing the jacket over the epicardial surface of the heart. The apicalend of the jacket can be a continuous surface which covers the apex ofthe heart. Alternatively, the apex of the jacket can have an openingthrough which the apex of the heart protrudes.

A cardiac reinforcement jacket, as disclosed herein, is not aninflatable device that surrounds the heart. Rather, the device istypically a single layer of biomedical material. In one embodimentdiscussed below, an inflatable member can be included with the device,but the inflatable member serves to reduce the volume within a localizedregion of the jacket and does not follow the entire jacket to surroundthe epicardial surface of the heart.

In one embodiment, the CRD jacket can be secured to the epicardium by asecuring arrangement mounted at the base of the jacket. A suitablesecuring arrangement includes, for example, a circumferential attachmentdevice, such as a cord, suture, band, adhesive or shape memory elementwhich passes around the circumference of the base of the jacket. Theends of the attachment device can be fastened together to secure thejacket in place. Alternatively, the base of the jacket can be reinforcedfor suturing the base of the jacket to the epicardium.

Various sized CRD jackets can be prepared such that different sizedjackets are used for different predetermined cardiac expansion sizes orexpansion ranges. Alternatively, a CRD jacket can include a mechanismfor selectively adjusting the size of the jacket. A mechanism forselectively adjusting the volumetric size of the jacket theoreticallyprovides for a "one size fits all" device. More importantly, however, anadjustable jacket provides the ability to titrate (readjust) the amountof cardiac reinforcement by graded reduction in jacket size astherapeutic reduction of cardiac expansion occurs.

A mechanism for selectively adjusting the size of the jacket can includea slot which opens at the base of the jacket and extends toward the apexend of the CRD. If the apex end of the CRD jacket is open, the apicalextent of the slot can be continuous with the apex opening. The slotincludes opposing lateral edges. By adjusting the proximity of theopposing lateral edges, the overall size of the jacket can be varied.Moving the opposing edges of the slot closer together narrows the slotand reduces the volumetric size of the jacket. The opposing edges of theslot can be fastened together at a predetermined proximity by, forexample, one or more lateral attachment devices, such as a cord, suture,band, adhesive or shape memory element attached to each lateral edge.

In another embodiment, a mechanism for selectively adjusting the size ofthe jacket can be an inflatable member. According to this embodiment,the inflatable member is mounted between the jacket and the epicardium.The volumetric size of the jacket can be reduced by inflating theinflatable member through an inflation port with, for example, a gas orliquid. As cardiac expansion volume responds to cardiac constraint bysize reduction, the predetermined size of the jacket can then be reducedby inflating the inflatable member within the jacket. Once inflated, thesize of the inflatable member is preferably maintained until therapeuticresponse causes a need for further inflation. According to theinvention, the inflation of the inflatable member provides a reductionin the predetermined size of the jacket by a fixed increase in volume ofthe inflatable member. The inflatable member is not rhythmicallyinflated and deflated to provide assistance to cardiac contractionduring systole.

The biomedical material of the invention can be radioluscent orradiopaque. In one embodiment, the material of the jacket can be maderadiopaque by inclusion of radiopaque markers for identification of theoutside surface of the heart, the expansion slot or inflation port. Asused herein, radiopaque means causing the CRD to be visible on x-ray orfluoroscopic viewing. Suitable radiopaque markers include, for example,platinum wires, titanium wires and stainless steel wires.

A CRD according to the present disclosure provides a new method for thetreatment of cardiac disease. As used herein, cardiac disease includesdiseases in which dilation of one of the chambers of the heart is acomponent of the disease. Examples include heart failure orcardiomyopathy. Heart failure can occur as a result of cardiac dilationdue to ventricular hypertrophy or secondary to, for example, valvularincompetency, valvular insufficiency or valvular stenosis.Cardiomyopathy, according to the invention, can be primary or secondaryto infection, ischemia, metabolic disease, genetic disorders, etc.

It is foreseen that constraint of cardiac expansion by a device of theinvention can provide reduced cardiac dilation. Reduced cardiac dilationcan cause reduction in the problems associated with cardiac dilationsuch as arrhythmias and valvular leakage. As reduction of cardiacdilation occurs, selective reduction of the predetermined size of thejacket also provides continued reinforcement for the size reduced heart.

A CRD jacket can also be used to measure cardiac performance. Accordingto this embodiment, the CRD jacket is rendered radiopaque by use of aradiographic marker. The radiographic markers are distributed throughoutthe jacket over the surface of the heart. By evaluation of the markersrelative to one another with each heart beat, cardiac performance may bemeasured. As such, evaluation of cardiac performance may assist inadjusting the predetermined size of a CRD jacket.

A CRD as described herein can be applied to the epicardium of a heartthrough a thoracotomy or through a minimally invasive procedure. For aminimally invasive procedure a CRD placement tool can be used to applythe CRD over the epicardium of the heart through a thorascopic incision.According to this embodiment, a CRD placement tool includes a cannula, astiff rod or wire and a guide tube. For placement of a CRD, the wire isthreaded through the guide tube which is passed around the circumferenceof the base of the jacket. The CRD with wire and guide tube passedthrough the base opening are then passed into the cannula. The cannulais of sufficient length and diameter to enclose the CRD, wire and guidetube during passage of the placement tool through a thorascopicincision. The placement tool is passed into the thoracic cavity andpositioned at a point near the apex of the heart. When in position, thewire and guide tube are pushed out of the cannula away from theoperator. Once outside the cannula, the wire and guide tube sufficientlyexpand the opening of the base of the CRD jacket to pass over theepicardial surface of the heart. When the CRD jacket is in position overthe epicardial surface, the wire, guide tube and cannula can be removed.A second incision can then be made to provide access for suitablesurgical instruments to secure or adjust the size of the CRD.

The invention will now be further described by reference to thedrawings.

FIG. 1 is a frontal view of one embodiment of a cardiac reinforcementpatch 1. The CRD patch 1 shown here is a mesh biomedical material 2having a thickened peripheral ring 3 which reinforces the peripheraledge 4 of the patch for attachment of the patch to the epicardialsurface of the heart.

FIG. 2 is a perspective view of a CRD patch 10 in place on theepicardial surface of a heart 11, for example, over a cardiac aneurysm(not shown) of the heart. In one preferred embodiment, the patch 10 issized to cover the extent of the cardiac aneurysm and is placed on theepicardial surface of the heart 11. In practice, the thorax issurgically opened and the region of the heart 11 with the aneurysm (notshown) is located and exposed. The patch 10 is placed over the aneurysmand sutured in place around the periphery 12 of the patch to providesufficient constraint to prevent further dilation of the aneurysm.

FIG. 3 is a perspective view of one embodiment of a CRD jacket 15according to the invention. According to the embodiment shown, thejacket 15 is a mesh material 16, and includes a circumferentialattachment device 17 at the base end 18 of the CRD jacket. The apex end24 of the jacket 15 is closed. The jacket 15 shown also includes a slot19 having opposing lateral edges 20 and 21, and fasteners (e.g. lateralattachment device 22 and 23) for selectively adjusting the volumetricsize of the jacket 15. The CRD jacket 15 shown also includes radiopaquemarkers 25 for visualizing the surface of the heart through radiographicstudy.

FIG. 4 is an alternative embodiment of a CRD jacket 30. Similar to theembodiment shown in FIG. 3, the embodiment of FIG. 4 includes a base end31 and an apex 32 end. The base end includes a circumferentialattachment device 33 for securing the CRD jacket 30 to the heart. TheCRD jacket 30 of FIG. 4 also includes a slot 34 having opposing lateraledges 35, 36. The lateral edges 35, 36 are shown pulled together at 37by a lateral attachment device 38, for example, a suture. In contrast tothe embodiment shown in FIG. 3, the embodiment shown in FIG. 4 has anopening 39 at the apex end 32 of the CRD jacket 30.

FIG. 5 is a perspective view of a CRD jacket 40 around a heart 41.According to the embodiment shown, at the base 42 of the jacket 40,there is a circumferential attachment device 43 which secures the CRDjacket 40 near the base of the heart 44. A slot 45, is shown withopposing lateral edges 46, 47 fastened together by a lateral attachmentdevice 48. In the embodiment shown, the CRD jacket 40 has an opening 49at the apical end 50 of the jacket. The apex of the heart 51 protrudesthrough the opening 49 at the apical end 50 of the jacket 40.

Still referring to FIG. 5, in a preferred embodiment, if one or more ofthe lateral attachment device 48 are made of an elastic material, suchas silicone rubber, the device can provide a way of applying a gradedconstraint around the outside of the heart 41 to reduce cardiac dilationover time. In practice, the jacket would be placed over the heart 41 asshown, either over or under the parietal pericardium (not shown). Thecircumferential attachment device 43 and lateral attachment device 48would then be tightened to cause a constraining effect on the outside ofthe heart.

In a preferred embodiment, if one or more of the lateral attachmentcords 48 is made of an elastic material, such as silicone rubber,surface pressure exerted on the epicardial surface of the heart variesas a function of the amount of dilation of the heart. This variablepressure has the effect of reducing the cardiac dilation to a certainpoint and then stopping because the surface pressure drops to anegligible amount. The amount of constraint or reduction in dilationthat is accomplished over time and the resultant cardiac performance maybe monitored radiographically using techniques known in the art, forexample fluoroscopy, by observing radiographic markers (FIG. 4, 25), ifpresent.

FIG. 6 is a schematic cross sectional view of an alternative embodimentof an arrangement for selectively adjusting the predetermined size of ajacket 53. According to this embodiment, an inflatable member 54 isinserted within the jacket 53 between the jacket 53 and the epicardialsurface 55 of the heart 56. The inflatable member 54 includes a fillingapparatus 57 for entry of a fluid (liquid or gas) to inflate theinflatable member 54 and reduce the predetermined size of the jacket 53.

FIG. 7 is a perspective view of a placement tool 60 which can be usedfor placement of a CRD jacket 61 around the epicardium of the heart. Asshown here, the base end of the jacket 62 is held open by guide tube 63through which is passed a wire or stiffening rod 64. The wire 64 can beremoved from the guide tube 63 by pulling on the wire extraction grip66. The placement tool 60 includes a cannula 65 which encloses thejacket 61, guide tube 63 and wire 64 during insertion of the tool into athorascopic incision.

FIG. 8 is a perspective view of a placement tool 70 being employed toplace a jacket 71 over the heart 72 on the outside of the parietalpericardium 73. The placement tool 70 is guided through a small incisionin the thorax and the jacket 71 is maneuvered into position over theheart 72. Once the jacket 71 is in proper position, the wire 74, whichis passed through the guide tube 75 around the base 76 of the jacket 71,is extracted from the guide tube 75 by pulling on the wire extractiongrip 77. The guide tube 75 is then extracted by pulling on the guidetube extraction grip 78. The cannula 79 is removed from the chest andthe circumferential attachment cord (not shown in this view), and thelateral attachment cord 80 can be fastened to secure the jacket 71.

The above specification and drawings provide a description of a cardiacreinforcement device and method of using on the heart. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention resides in the claimshereinafter appended.

What is claimed is:
 1. A cardiac reinforcement device, said devicecomprising:(a) a cone-shaped biomedical material having an apical endand a based end and which generally conforms to the external geometry ofa patient's heart; (b) said cone-shaped biomedical material comprising aplurality of open cells, each open cell defined by multiple sides, eachopen cell sharing at least one of said multiple sides with an adjacentopen cell; (c) said cone-shaped biomedical material having apredetermined size selected to surround the surface of the heart andconstrain cardiac expansion beyond a predetermined limit.
 2. The cardiacreinforcement device according to claim 1 wherein said cone-shapedbiomedical material is substantially non-elastic.
 3. The cardiacreinforcement device according to claim 1 wherein said cone-shapcdbiomedical material has a lateral slot providing for selectiveadjustment of a circumference of said cone-shaped biomedical material tosaid predetermined size.
 4. The cardiac reinforcement device of claim 3further comprising an inflatable member sized for selectively adjustingsaid predetermined size of said cone-shaped biomedical material, saidinflatable member sized for positioning between said device and saidpatient's heart.
 5. The cardiac reinforcement device according to claim1 wherein said apical end of said device is open.
 6. The cardiacreinforcement device according to clam 1 wherein said biomedicalmaterial is a polyester mesh.
 7. The cardiac reinforcement deviceaccording to claim 1 wherein said base end of said cone-shapedbiomedical material includes a securing arrangement for securing saiddevice to said patient's heart.
 8. A cardiac reinforcement device forconstraining cardiac size during diastole, said device comprising:(a) asubstantially non-elastic biomedical material for contacting anepicardial surface of a patient's heart and configured tocircumferentially surround said epicardial surface of said patient'sheart; (b) said configured biomedical material having a base end and anapical end and formed into a jacket to surround the heart with thejacket having an internal volume to receive said heart; (c) saidnon-elastic biomedical material comprising a continuous meshconstruction, said continuous mesh construction defining a plurality ofopen cells; and (d) said configured biomedical material providingcardiac constraint during diastole without substantially assistingcardiac contraction during systole.
 9. The cardiac reinforcement deviceaccording to claim 8 wherein said configured biomedical material has alateral slot for providing selective adjustment of a circumference ofsaid biomedical material to a predetermined size.
 10. The cardiacreinforcement device according to claim 9 wherein said slot has opposinglateral edges which decrease said predetermined size of saidcircumference of said biomedical material by moving said opposinglateral edges together.
 11. The cardiac reinforcement device accordingto claim 8 wherein said apical end of said device is open.
 12. Thecardiac reinforcement device according to claim 3 whercin saidbiomedical material is a polyester mesh.
 13. The cardiac reinforcementdevice according to claim 8 further comprising an inflatable membersized for selectively adjusting said predetermined size of saidbiomedical material, said inflatable member sized for positioningbetween said biomedical material and said patient's heart.
 14. A cardiacreinforcement device for treating a cardiac condition, said dcvicecomprising:(a) a synthetic biomedical material having interconnectedsides with a predetermined maximum spacing between said sides which canbe disposed on diametrically opposed surfaces of a heart; (b) saidsynthetic biomedical material comprising a continuous mesh construction,said continuous mesh construction defining a plurality of open cells;(c) said biomedical material having a base end and an apical end; and(d) said biomedical material providing cardiac constraint duringdiastole without substantially assisting cardiac contraction duringsystole.
 15. The cardiac reinforcement device according to claim 14wherein the biomedical material circumferentially surrounds the heart.